The WHTC test is a transient engine dynamometer schedule defined by the global technical regulation (GTR) No. 4  developed by the UN ECE GRPE group . The GTR is covering a world-wide harmonized heavy-duty certification (WHDC) procedure for engine exhaust emissions. The regulation is based on the world-wide pattern of real heavy commercial vehicle use. Two representative test cycles, a transient test cycle (WHTC) with both cold and hot start requirements and a hot start steady-state test cycle (WHSC), have been created covering typical driving conditions in the EU, USA, Japan and Australia.
The WHTC is a transient test of 1800 s duration, with several motoring segments. Normalized engine speed and torque values over the WHTC cycle are schematically shown in Figure 1.
Figure 1. World Harmonized Transient Cycle (WHTC)
Note: Negative torque values are arbitrary representation of closed rack motoring